1. Field of the Invention
This invention relates to an improved battery plate for an electrical storage battery. More particularly, this invention relates to the method and apparatus of an improved battery plate fabricated with a fused web of metallic fibers.
2. Background of the Invention
For over one hundred years, electric storage batteries have provided portable and instantaneous electric power for a variety of electrical devices. Electric storage batteries include an anode and a cathode fabricated from dissimilar materials with an electrolyte interposed therebetween. An ionic exchange between the anode and the cathode through the electrolyte generates an electrical potential between the anode and the cathode. When the anode and the cathode are interconnected by an external load, an electric current is provided through a flow of ions through the electrolyte.
The electrical potential produced between the anode and the cathode is determined by the dissimilar materials used for constructing the anode and the cathode. The current produced by an electric storage battery is partially determined by the surface area of the anode and the cathode.
All electric storage batteries have an internal resistance which limits the maximum current flow that can be generated by the electric storage battery. The maximum current flow that can be generated by the electric storage battery is commonly referred to as short circuit current. The short circuit current is the maximum current the electric storage battery can produce when the anode is externally shorted to the cathode with a large conductor.
In an effort to increase the surface area of the anode and the cathode, many electric storage batteries use a plurality of anode and cathode pairs within each battery cell. A separator is interposed between each anode and cathode pair with the anodes and cathodes being respectively connected in electrical parallel within each cell. The plurality of anode and cathode pairs within each battery cell increases the surface area of the anode and cathode for increasing the short circuit current of the cell.
In many cases, the anode and the cathode are each fabricated from a combination of materials in an effort to reduce the weight and cost of the electric storage battery and to increase the efficiency thereof. In such cases, each of the anode and the cathode is fabricated with a conductive battery plate having a multiplicity of pores for receiving an active material therein.
Typically the battery plate is fabricated from a metallic material defining a multiplicity of pores for receiving all active material therein. In some cases, the battery plate is fabricated from an insulating material coated with a conductive material. The insulating material defines a multiplicity of pores for receiving an active material therein.
The battery plate must be mechanically strong in order to maintain the active material within the multiplicity of pores within the battery plate. Under certain conditions, a vibration and other mechanical impacts may cause the active material to dislodge or separate from the battery plate thereby reducing efficiency of the electrical storage battery.
In some electric storage battery configurations, the battery plates including the active material are rolled to form a cylindrical configuration to provide a cylindrically shaped electric storage battery. During the rolling process, the battery plates and the active material are subjected to substantial stresses during the rolling process. Any fracture of a portion of the battery plate will result in a reduced conductivity of the battery plate and accordingly a reduction in the current output of the electric storage battery.
Many portable devices of the prior art utilize rechargeable batteries such as nickel cadmium, nickel hydride and other types of rechargeable batteries which enable the battery to be discharged and recharged hundreds or in some cases thousands of times. A rechargeable battery must be designed and fabricated to withstand the charging and recharging as well as an extended life of the rechargeable battery.
In addition, the prior art is striving to continue to reduce the weight of batteries in order to reduce the overall weight of many portable device such as radios, televisions, telephones, computers, games and the like. In order to reduce the weight of the battery, the prior art has utilized various materials for the battery plates of electric storage batteries.
U.S. Pat. No. 3,262,815 to Langer et. al. discloses an electrode suitable for a secondary battery comprising a plate formed from a compact body of intermingled fine metal fibers, the majority of the fibers extending the full height of the plate and a small proportion extending transverse thereto, the fine metal fibers having a generally parallel lineal orientation in one direction and an active electrode material distributed on and disposed within the body of the metal fibers, a liquid electrolyte permeable sheet wrapping enclosing the plate, an electrical contact attached to the plate transverse to the general lineal orientation of the fine metal fibers whereby most of the fibers are directly connected thereto, an electrical lead attached to the electrical contact, and an insulated covering about the lead and the contact.
U.S. Pat. No. 4,206,271 to Norling el. al. discloses a method for the manufacture of a highly porous nickel electrode body for electrical accumulators. The new electrode body is also disclosed. By using 5-7% volume of a nickel powder in admixture with 93-95% by volume of a pore-forming agent selected from the group consisting of ammonium bicarbonate and ammonium carbonate when pressing and sintering the electrode body a very high porosity is obtained, such as 90-95%, in spite of which the mechanical strength of the body is so high as to resist the strains of an accumulator cell. Especially preferable to impart outstanding strength to the electrode body, is a pressure of at least 100 MPa in the pressing operation.
U.S. Pat. No. 4,251,603 to Matsumoto et. al. discloses a battery electrode comprising a plaque made of a sponge-like porous metal matrix having a multiplicity of cells connected with each other in three-dimensions, wherein the sectional area of the gratings making up the sponge-like metal porous plaque decreases continuously along the thickness of the plaque from the surface toward the central part and an active material is impregnated in the porous plaque.
U.S. Pat. No. 4,628,593 to Fritts et. al. discloses a low shear battery plaque and a nickel electrode fabricated therefrom, the latter consisting essentially of a centrally located layer of a conductive felt, layers of sintered nickel on each side of the felt and nickel hydroxide active material disposed throughout the pores of the sintered nickel.
U.S. Pat. No. 5,080,963 to Tatarchuk et. al. discloses a new class of composite results from a matrix of carbon fibers, including graphite fibers, interwoven in a network of fused metal fibers. The composites can be fabricated to have varying surface area, void volume and pore size while maintaining high electrical conductivity. Composites are readily prepared from a preform of a dispersion of carbon fibers, metal fibers, and an organic binder such as cellulose, by heating the preform at a temperature sufficient to fuse the metal fibers and to volatilize at least 90% of the binder with a loss of less than about 25%, and usually under 10%, by weight of carbon fiber.
U.S. Pat. No. 5,106,707 to Catotti et. al. discloses a sealed rechargeable nickel electrode containing an electrochemical cell having a pasted negative electrode with paste layers adhered to a nonforminous conductive substrate, which retards growth (swelling) of the nickel electrode on cycling.
U.S. Pat. No. 5,200,281 to Leap et. al. discloses a sintered bipolar battery plate (10) which is made containing two porous electrodes and a central, non-porous, metallic cell separator-current collector sheet (12) where the positive electrode contains sintered particles (14) of elemental silver sintered into an expanded metal sheet (18) and the negative electrode contains sintered particles (16) of elemental iron sintered into an expanded metal sheet (18), where the positive and negative electrodes are sintered to a thin, porous, metallic connection layer (20) selected from at least one of nickel fiber or nickel powder, which is sintered to the current collector (12). This plate (10) can be placed in a case (22) containing alkali hydroxide electrolyte and having metal end plates (29) for electrical connections.
U.S. Pat. 5,200,282 to Masuhiro et. al. discloses a nickel electrode for use in an alkaline battery using a network-like alkaline-proof metal mesh having pores at the inside thereof as a core metal current collector, as well as an alkaline battery using such a nickel electrode. Inexpensive nickel electrode having high performance, great capacity can be obtained at high productivity.
U.S. Pat. No. 5,244,758 to Bronoel et. al. discloses a positive nickel electrode having a structure of cellular nickel foam filled with a paste based on nickel hydroxide. The paste contains (in dry matter and per 100 parts by weight nickel hydroxide) 7 to 8 parts by weight powder-form nickel metal, 5 to 12 parts by weight of a cobalt hydroxide and/or salt, the parts by weight being expressed as equivalents of cobalt metal.
Although the aforementioned prior art have advanced the battery art, there is a need for further advancement in the battery art especially in the fabrication of the battery plates therefore.
Therefore, it is an object of this invention to provide an improved battery plate for an electric storage battery fabricated of a matrix of randomly oriented metallic fibers wherein the metallic fibers are fused to adjacent fibers to provide an electrically conductive porous battery plate with a high total energy density as well as high strength.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a matrix of randomly oriented metallic fibers wherein the metallic fibers are sintered to fuse the metallic fibers into an electrically conductive porous battery plate.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers wherein each of the metallic fibers have a substantially equal length and a substantially uniform cross-sectional area.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers wherein each of the metallic fibers has a substantially cylindrical shape for increasing the surface area of the battery plate.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers for providing a multiplicity of pores defined between adjacent fibers.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers for providing a multiplicity of pores defined between adjacent fibers for interlocking an active plate material into the multiplicity of pores of the battery plate.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers for providing a battery plate wherein the porosity of the battery plate can be accurately controlled.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers comprising a multiplicity of major diameter fibers and a multiplicity of minor diameter fibers sintered to provide a highly conductive battery plate.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers with increased porosity and increased conductivity over the battery plates known to the prior art.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers having a higher porosity and capable of receiving substantially more active plate material than the battery plates of the prior art.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers having a porosity of greater than 95 percent.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers which may be rolled in a cylindrical configuration without deterioration of the electrical contact or bond between adjacent fused metallic fibers.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers with the metallic fibers having one or more diameters uniformly distributed within the matrix.
Another object of this invention is to provide an improved battery plate for an electric storage battery fabricated of a sintered matrix of randomly oriented metallic fibers wherein the metallic fibers may be preferentially disposed in the battery plate for providing a substantially uniform current density throughout the battery plate.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention, the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.